Process for improving the acid dye receptivity of polylactams and polylactam products so produced



United States Patent US. Cl. 26078 Claims ABSTRACT OF THE DTSCLOSUREProcess of improving the acid dye receptivity of polycaprolactam and theresulting product wherein there is homogeneously incorporated in thepolycaprolactam a small amount of (a) a phosphoric acid ester or analkyl or aryl phosphonic acid or an ester thereof, and (b) an alkylenepolyamine. The product exhibits improved receptivity for acid dyes witha minimum reduction of its solution viscosity.

This invention relates to a process for improving the dye receptivity ofpolylactams for acid dyes, and more particularly, the invention isdirected to a process of incorporating a combination of certain organicphosphorous compounds and amines into a fiber-forming polylactam,especially polycaprolactam, so as to obtain a product which is easilyspun into textile fibers and which can be dyed in an improved mannerwith acid dyes.

It is known that the dye receptivity of fiber-forming polyamides foracid dyes can be improved if the polyamide is initially treated so as tocontain an increased number of amino end groups. One method of achievingthis result has been to add free amines to the polyamide-forming initialmaterials prior to polycondensation. Suitable amines which have beensuggested for this purpose include aliphatic monoamines or diamines andheterocyclic amines. Where the polyamide is obtained by polycondensationof dicarboxylic acids and diamines, e.g., in the preparation ofpolyhexamethylene adipamide, only a small excess of the above-noted freeamines is necessary. On the other hand, a considerably greater amount ofthe free amines must be added when using lactams as the monomers in theformation of a fiber-forming polyamide. The polyamides which areproduced according to this known process and which show a higher numberof amino groups are not fully satisfactory because they are moredifficult to spin into filaments or fibers. For example, if one wishesto obtain an appreciable improvement in dyeability and correspondinglyadds larger amounts of the amine, the resulting polyamide has asubstantially lower viscosity and the molten polyamide tends to dripduring spinning, so that a spinning of the polyamide melt into filamentsis no longer practical.

According to another known process, this defect in the polyamide causedby the addition of the amine is supposed to be avoided by addingphosphorous compounds to the polyamide prior to spinning. Suitablephosphorous compounds suggested for this purpose are hypophosphites ofalkali and alkaline earth metals as well as those of zinc, cadmium,manganese, aluminum and tin, and also salts of phosphinic acid.According to still another known process, the dye receptivity ofpolyamides is supposed to be improved by the addition of alkyloraryl-phosphinic acids or their amine salts. It has become apparent thatthe addition of such compounds, particularly the amine salts ofphosphinic acids, results in an appreciable improvement of the dyereceptivity whereas the metal salts of phosphinic acid do not have anyefiect. In any case, the known processes are restricted to polyamidesprepared from dicarboxylic acids and diamines. If one attempts to applythese additives to polyamides formed from lactams, then it has beenfound that only a slight and unimportant improvement in dye receptivityis possible.

One object of the present invention is to provide a process whereby asubstantially improved acid dye receptivity can be imparted to afiber-forming polylactam without impairing the subsequent spinning ofthe polymer into filaments.

Another object of the invention is to provide a process for improvingthe receptivity of a fiber-forming polylactam for acid dyes by using anovel combination of additives which can be easily incorporated into thepolylactam either before or during polycondensation of the lactammonomer or subsequently to the polylactam before it is spun into textilefibers.

These and other objects and advantages of the invention will become moreapparent upon consideration of the following detailed specification.

It has now been found, in accordance with the invention, that theforegoing objects can be achieved by homogeneously incorporating into afiber-forming polylactam: (a) about 0.05 to 3 0 by weight, preferablyabout 0.1 to 2% by weight, of an organic phosphorous compound selectedfrom the group consisting of phosphoric acid esters and alkyl and arylphosphonic acids and their esters; and (b) about 0.01 to 1% by weight,preferably 0.02 to 0.5% by weight, of a polyamine of the formula whereinm represents an integer of O to 3, n represents an 1nteger of 2 to 6 andthe sum of m and n is not more than 6 The term dye receptivity isemployed herein with reference to the ability of the polymer fiber toabsorb or take up an acid dye during any conventional method of dyeing.The polylactams which are improved by the proc ess of this invention arewell known fiber-forming polymers containing recurring NHCO groupsconnected by an alkylene group in the polymer chain. Polycaprolactam,sometimes referred to as nylon 6, is most often used for commercialtextiles, and the production of the polyamide fromthe monomeric lactam,such as epsiloncaprolactam is quite well known and requires no furtherexplanation.

The two essential additives of the invention, i.e., the organicphosphorous compound and the polyamine can be introduced andincorporated into the polycaprolactam at any point prior to spinningfilaments or fibers therefrom, under conditions which ensure anhomogeneous mixture of the polymer and the additives, e.g., by thoroughmixing during polycondensation or by kneading and homogenizing theadditives with the molten polymer in an extruder or similar mixingdevice. Thus, the additives may be introduced before thepolycondensation of the lactam monomer or at any suitable time duringthe polycondensation reaction. Moreover, it is possible to admix the twoessential components of the invention with the polylactam product, whichis in the form of cuttings, granules or small pellets at a point priorto spinning, e.g., by panniering the cuttings or otherwise surfacecoating the polymer particles. Thereafter, the organic phosphorouscompound and the polyamine are homogeneously mixed with the polylactamby any conventional method, e.g., by reextruding the treated material ina screw extruder or even in a mixing section just preceding the meltspinning operation.

As the organic phosphorous compound employed as component (a) in theprocess of the invention, it is particularly desirable to employ thosecompounds of the formula in which X stands for aryl or alkyl, preferablyphenyl and lower alkyl such as methyl, ethyl, propyl or butyl, X standsfor aryl such as phenyl, aralkyl such as benzyl or lower alkyl, i.e.,alkyl of 1 to 4 carbon atoms, and Y stands for hydrogen, aryl such asphenyl, or lower alkyl of 1 to 4 carbon atoms. Specific organicphosphorous compounds suitable for the purposes of the invention can belisted as follows:

Tributyl phosphate Methanephosphonic acid dimethyl esterEthanephosphonic acid diethyl ester Phenyl-methancphosphonic aciddiethyl ester Tripropylphosphate Triethylphosphate TrimethylphosphateTriphenylphosphate Phenyl-methanephosphonic acid dibutyl esterPhenyl-methanephosphonic acid diphenyl ester Benzenephosphonio acidBenzenephosphonic acid dibutyl ester Benzenephosphonic acid diphenylester Ethanephosphonic acid As to the amine component (b), the bestresults are achieved in accordance with the invention by using acompound of the formula in which p stands for an integer of 2 to 4,i.e., diethylene triamine, triethylene tetramine and tetraethylenepentamine. In addition, the following specific polyamines are alsosuitable:

Hexamethylene diamine Pentamethylene diarnine Tetramethylene diamineTrimethylene diarnine Ethylene diamine Dipropylene diamine Tripropylenetetramine Tetrapropylene pentamine Dibutylene triarnine Tributylenetetramine Dipentylene triamine If a phosphoric or phosphonic acid esterof the invention is added alone for increasing the .acid dye receptivityof the polylactam, then some increase in dyeability does takeplace-although it is proportionately less than that achieved by theprocess of the invention. Even this effect cannot be achieved with theknown phosphinic acids or phosphinic acid derivatives when they .areused with a polylactam.

On the other hand, even when using the organic phosphorous compounds ofthe present invention, the acid dye receptivity cannot be furtherincreased simply by the addition of larger amounts of this componentbecause the viscosity of the polylactam is then simultaneously reduced.However, if one introduces a mixture of the phosphoric or phosphonicacid ester together with a small amount of the polya-mine as the secondcomponent, within the proportions defined by the invention, then theacid dye receptivity of the polylactam increases quite sharply in a verysurprising manner. Although the amines just as the organic phosphorouscompounds cause a lowering of the viscosity, it has been found that adefinite synergistic effect takes place with the dye receptivityincreasing much more rapidly than any accompanying decrease inviscosity. Thus, one can obtain an optimum improvement of dye aflinityor receptivity with the least possible reduction of viscosity by thesuitable selection of the phosphorous compounds and amines as well as bychoosing appropriate amounts of these compounds within the prescribedlimits of the invention. In this respect, the preferred polyethylenepolyamines as noted above offer the greatest advantage because theyyield a very substantial increase in dye absorption even when usingquite small amounts, and these small amounts of the polyamine have onlya slight influence on the viscosity.

Especially favorable results are achieved according to the invention ifthe organic phosphorous compounds and amines are added to the completelycondensed polylactam prior to spinning into filaments. When the processof the invention is carried out in this manner, there is practically noinfluence on the viscosity of the polymer. Surprisingly, however, theimprovement in the acid dye receptivity is considerable. This result wasnot at all expected because it had been previously assumed that in orderto increase the number of amino end groups, it would be absolutelyessential to introduce any additives especially aminesinto the initialmonomeric materials.

The invention is further illustrated by without being limited to thefollowing examples. In these examples as well as in the appended claimsand elsewhere in this specification, the percentages of the phosphorousand amine compounds are by weight with reference to the particularlactam or polylactam which is being treated. The solution viscosity ismeasured in each instance by measuring the flew rate of a 1% solution ofthe polylactam in formic acid. Extinction values are obtained byconventional measurement of the dye solutions.

EXAMPLE I While caprolactam is being polycondensed in a conventionalmanner, there is added to the fluid monomer 1% by weight ofethanephosphonic acid diethyl ester and 0.3% by weight of diethylenetriamine. The resulting polyamide has a solution viscosity of 2.05 andhas good spinning qualities. In order to ascertain the dyeingimprovement which has been achieved, filaments of the polyamidecontaining the above named additives are dyed together with polyamidefilaments which contain no additives in the same bath with the acid dyeAnthralan Blue B. The dye absorbed from the bath by the two filamentsamples is thereafter completely extracted with a pyridinewater mixture.The extinction of both dye solutions is measured, and amounted to aproportion of 1:3.8 (polyamide without additiveszpolyamide+phosphorouscompound +amine) As described in the above example, further tests werecarried out while changing the additive compounds or their proportionsas summarized in the following table:

the solution viscosity of the additive-containing cuttings compared tothe normal polyamide is somewhat lower,

TABLE I Percent Solution Extinction Additives by viscosity proportionweigh Test Number:

1 Ethanephosphonic diethyl ester 1.0 2 05 1 3 8O "i g g h i 3 anep ospeuro 2101 re y "{Diethylene triamine 0.4 i 1 3 {Ethanephosphonic aciddiethyl es 0.1 2 14 1 2 34 gtefiametlhylefie diamigeafilnfuy 0.3

anep osp onic aci 1e y es en iHexamethylene diamjne 5 15 1 27{Ethanephosphonic acid diethyl ester: 0.7 2 14 1 3 05 Hexamethyleuediamine 0.3

Ethanephosphonie acid diethyl ester 1.0 l 2 06 1 2 93 Hexamethylenediamine 0.3 J

Ethanephosphonic acid diethyl este 1 5 1 90 1 2 83 Hexamethylene diamineEthanephosphonic acid diethyl ester- 2.0 1 90 1 2 95'"ilgekilrametllliylege diamigeanfi; 1 .i 0.3

t anep osp onic aci ie y es en 9 "illgielilrametlhylegediamigeaifilflfuiuu 5 05 1 30 t anep osp onic aci e y es er 10"{lgagametliliylefie diamireaufii 1 E s 0 99 1 35 anep osp onic aci ie yes er 1.5 n '{gerlamethlylenlei diaminefa flt fi i t $5 89 1 80 l e aneposp onic aci ime y es er 12 "{DiethyIene triamine 0. 3 05 1 31 13 1Phenyl-methanephosphonic acid dimethyl ester- 2. 5 2.01 1 1. 65 14 1Etf."t'"t "ha em? "'i'6" t anep osp omc aci 1e y es er 15 irifthyltlilnetitramineafii EH1? I 0O 1 56 t anep osp onic aci e y es er 16"{Tetraethylene pentarm'ne 0.5 i 1 05 1 Comparative tests.

EXAMPLE II Dried polycaprolactam cuttings ready for spinning with asolution viscosity of 2.55 are mixed in a tumbler drier successivelywith 0.3% by weight of hexamethylene diamine and 1% by weight oftributyl phosphate. Thereafter, these cuttings are regranulated in anextruder. After the regranulation, the modified polycaprolactam exhibitsa solution viscosity of 2.53. The cuttings are then spun and theresulting filaments dyed as described in EX- ample I. By measuring theextinction proportion of the dyestuff extracted from each of thefilament samples, the dyeing improvement of the modified polyamide bycomparison with the unmodified polyamide is ascertained. The extinctionproportion in this case amounts to 1:2.63 (polyamide withoutadditive:polyamide-i-phosphorous compound-i-amine) As described inExample II above, further tests are carried out with changes in thecompounds or additive amounts as summarized in the following table:

an increase of the viscosity occurs in the spinning process. In thismanner, therefore, a very high viscosity of the finished filaments isassured. The addition of the amine, on the other hand, acts as aviscosity stabilizer and reduces the filament viscosity during thespinning process, thereby preventing an undesirably large increase inthe solution viscosity. Also, this eifect has proven to be certain asshown in the following tests.

EXAMPLE III TABLE II Percent Solution Extinction j Addltives by weightviscosity of proportion cuttings Test Number: T b t 1 h h t 1 riuypospae2.0 2 "{Hexamethylene diamine.-- 0. 3} 47 91 3 Tributyl phosphate 1.0 2.62 1:2. 13 4 Hexarnethylene diamine.. 0.3 2. 42 112.02

1 Comparative tests.

A further advantage of the process according to the invention is to beseen in the fact that during the spinning of 'the polyamide the addedphosphorous compounds cause a considerable after-condensation, so thateven if in Example I. Through the high increase of the solutionviscosity during the spinning, the effect of the phosphonic acid esterand amine added during the polymerization in lowering the solutionviscosity in substantially reduced.

The invention is hereby claimed as follows:

1. A process for improving the receptivity of a fiberformingpolycaprolactam for acid dyes which comprises: homogeneouslyincorporating into said polycaprolactam:

(a) about 0.05 to 3% by weight, with reference to the polycaprolactam,of an organic phosphorous compound selected from the group consisting ofphosphorie acid esters and alkyl and aryl phosphonic acids and theiresters, and

(b) about 0.01 to 1% by weight, with reference to the polycaprolactam,of a polyamine of the formula wherein m represents an integer of to 3, nrepresents an integer of 2 to 6 and the sum of m and n. is not more than6.

2. A process as claimed in claim 1 wherein (a) is used in an amount ofabout 0.1 to 2% by weight and (b) is used in an amount of about 0.02 to0.5% by weight.

3. A process as claimed in claim 1 wherein component (a) is a phosphoricacid ester of the formula X0 OX wherein X represents a substituentselected from the group consisting of lower alkyl and phenyl.

4. A process as claimed in claim 1 wherein component (a) is a compoundof the formula YO OY wherein X' represents a substituent selected fromthe 8 group consisting of lower alkyl, phenyl and benzyl and Yrepresents a suhstituent selected from the group consisting of hydrogen,lower alkyl and phenyl.

5. A process as claimed in claim 1 wherein component (b) is a compoundof the formula wherein p represents an integer of 2 to 4.

6. A process as claimed in claim 1 wherein component (b) ishexamethylene diamine.

7. A process as claimed in claim 1 wherein component (a) isethanephosphonic acid diethyl ester.

8. A process as claimed in claim 1 wherein component (a) ismethanephosphonic acid dimethyl ester.

8. A process as claimed in claim 1 wherein component (a) is tributylphosphate.

'10. The polylactam product obtained by the process of claim 1.

References Cited UNITED STATES PATENTS 2,241,322 5/194'1 Hanford 260-7-82,510,777 6/1950 Gray 260-78 2,557,808 6/1951 Walker 260-78 2,904,5369/1959 Reith 260-78 3,296,215 1/1967 Crovatt 260-78 3,296,216 1/ 1967Snooks 260-78 3,300,448 '1/ 1967 Gauthier et al. 260-78 WILLIAM H.SHORT, Primary Examiner.

H. D. ANDERSON, Assistant Examiner.

US. Cl. X.R. 260-78; 8-55 U.S. DEPARTMENT OF COMMERCE PATENT OFFICEWashington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,437,641 April 8, 1969 Jiirgen Lenz et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, line 10, "U 27,948" shouldread V 27,948

Signed and sealed this 21st day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

